DISCUSSION

PCP Disk Requirements --

J. White reported that PCP
development has progressed to the point of designing the disk
allocation layout for the processing of each scan. Each PCP (Pipeline
Control Processor) processes a single scan at a time, and each CPU on
each production machine (two machines, four CPUs each) will run one PCP
during the corresponding phase of the 2MAPPS execution. In order to
meet the goal of reducing I/O contention between PCPs, the current
design for each production machine calls for three input volumes (one
per band), four scratch volumes (one per CPU/PCP), and two output
volumes, hence nine disk volumes per machine. This is a change from the
previous requirement for eight disk volumes per machine; R. Cutri will
inform R. Scholey of the increased requirement. If CPUs are added to
a production machine with the intention of running more PCPs, then one
additional disk volume per additional CPU will also be required.

R. Beck reported that for testing in the near term, one karloff
disk volume could be used as a ninth lugosi volume (assuming PCP
testing on lugosi), but the karloff disk should be used as an input
volume, since reads across the karloff-lugosi connection are
significantly faster than writes.

Maintaining Products From Different Processing Dates/Times
--

2MAPPS subsystem cognizant engineers have recently been
encouraged to include the processing date and time in the output
headers of the files their subsystems generate (see the minutes to
meeting no. 93). T. Evans pointed out that the current data base design
contains no provision for storing multiple output file sets for the
same scan processed on different dates or times, and to add this
capability would complicate the indexing needed for the rapid accesses
which are the goal of the current design. Simply storing products in a
hierarchical scheme in which processing date is a level of the
hierarchy is not a solution that fits into the design contemplated.
The different processing dates/times would somehow have to be woven
into the indexing scheme, and a good way of doing that is not apparent.
Some team members felt that storing these different output sets in a
readily accessible fashion should be considered highly desirable. T.
Evans will study this matter further.

Extended Source CDR --

R. Cutri reported that the
Extended Source Critical Design Review will be held Wednesday, June 26,
and that a revised agenda schedule has been circulated. T. Chester
touched on some of the issues that will be raised. These included a
presentation showing that the "super coadd" (as known in galaxy
processing circles, i.e., multi-band, as opposed to multi-coverages in
a single band) is not required to meet project requirements, and that
it would be costly in terms of extra CPU time and suffers from
fundamental theoretical problems. A runthrough of presentations will be
held on Friday, June 21.

Effects of Varying Matched Filter and Smoothing Kernel on
DAOFind --

R. Cutri presented the results of some analysis he and
S. Wheelock have been doing to study the effects on DAOFind of varying
the FWHM of the matched filter and the smoothing kernel used in
producing the coadded image employed for aperture photometry. The M67
field was used in the study, which evaluated the completeness and
reliability as functions of the parameters varied. The dependence on
the matched filter FWHM was weak in the vicinity of the right value,
especially for slightly large values. The dependence on the H parameter
of the smoothing kernel was more involved: a value of 0.3 yielded
"peakier" point sources, so that more detections resulted, while a
value of 0.4 yielded fewer detections, but with a higher reliability,
so that the overall completeness did not suffer significantly. The
lower reliability of the 0.3 value was compensated by rejection
downstream, so that the bottom line was that any reasonable settings
produced more or less the same final result. A suggestion that H = 0.35
should be used was passed by acclamation.